# 按照for的思想，可以这么写
count = 0
for i in range(0, 1000, 7):
    print(i, end=' ')

    count += 1
    if count >= 20:
        break

# 将for改造成while：
count = 0
i = 0
while True:
    print(i, end=' ')

    i += 7
    count += 1
    if count >= 20:
        break

# 其实，按照while的思想，应该这么写
count = 0
i = 0

while count <= 20:
    print(i, end=' ')

    i += 7
    count += 1
